A method has conventionally been widely known in which an electroconductive paste composition is used in order to form an electrode, electrical wiring (wiring), or the like on a base, e.g., a film, substrate, or electronic component. Known as an example of such electroconductive paste compositions is a thermosetting composition including an electroconductive powder and a thermosetting resin. Specifically, for example, such a thermosetting electroconductive paste composition is applied to or printed on a base so as to result in a given conductor pattern and the coating film or printed film is then dried and hardened by heating. On the base is thus formed a hardened film as an electrode, wiring, or the like having the given conductor pattern.
Fields in which such thermosetting electroconductive paste compositions are used to form electrodes or wiring are not particularly limited, and the compositions can be used in various fields. Representative examples include the field where the conductor electrodes of a solar cell having an amorphous silicon layer are formed. Such a solar cell includes a collector electrode, such as a finger electrode or a busbar electrode, formed in a surface of a solar cell. Such collector electrodes are generally formed by printing an electroconductive paste composition on a surface of a solar cell by a printing technique, e.g., screen printing, and hardening the printed composition.
A known configuration of such thermosetting electroconductive paste compositions employ a silver powder as the electroconductive powder and an epoxy resin and/or a blocked polyisocyanate compound as the thermosetting ingredient. However, because of the expensiveness of silver, electroconductive paste compositions are being developed in recent years in which a powder of copper or a copper alloy (copper-based powder) or a silver-coated copper-based powder obtained by coating the surface of the copper-based powder with silver is used as a less expensive electroconductive powder.
For example, Patent Document 1 discloses a thermosetting electroconductive paste composition that includes an electroconductive powder, which is at least one of a silver-coated metal powder and a powder of either copper or an alloy thereof, and a thermosetting ingredient, which is at least one of an epoxy resin and a blocked polyisocyanate compound, and that further includes a benzotriazole compound, which is benzotriazole or a derivative thereof, and a phosphoric-ester-group-containing dispersant having a phosphoric ester group in the chemical structure, in respective amounts within given ranges.